1. Field of the Invention
The present invention relates to an apparatus for recovering a carrier from a photoreceptor belt of a liquid electrophotographic printer.
2. Description of the Related Art
Generally, liquid electrophotographic printers, applied to printers or photocopiers, print an image by applying a developer, in which a solid toner of a predetermined color is mixed with a liquid carrier acting as a solvent, to an electrostatic latent image formed on a photoreceptor medium such as a photoreceptor belt running along an endless track.
FIG. 1 is a schematic diagram illustrating the configuration of a conventional liquid electrophotographic printer. Referring to FIG. 1, a liquid electrophotographic printer includes a photoreceptor belt 10 which is supported by a plurality of guide rollers 11 and runs along an endless track, a plurality of development devices 13a, 13b, 13c and 13d, a drying unit 20 and a transfer roller 16.
The photoreceptor belt 10 is charged to a predetermined potential at a charging station 15. The potential of the photoreceptor belt 10 changes depending on beams emitted from a plurality of laser scanning units 14a, 14b, 14c and 14d which are installed in close proximity to the respective development devices 13a, 13b, 13c and 13d, so that an electrostatic latent image is formed on the photoreceptor belt 10. The development devices 13a, 13b, 13c and 13d allow a developer, in which a toner is mixed with a liquid carrier, to selectively adhere to an electrostatic latent image area on the photoreceptor belt 10. Toners T are supplied to a transfer roller 16, and then transferred to printing paper P passing between the transfer roller 16 and a fixing roller 17 due to a difference in surface energy.
The drying unit 20 includes a drying roller 22 and heating rollers 24. The drying roller 22 absorbs the liquid carrier from the photoreceptor belt 10 which has passed the development devices 13a, 13b, 13c and 13d. The heating rollers 24 assist the function of the drying roller 22 by evaporating the liquid carrier absorbed by the drying roller 22. Since the evaporated carrier negatively affects the human body, it is necessary to prevent the evaporated carrier from effusing to the air. Moreover, it is necessary to recover the carrier in order to reduce the consumption of the carrier so that costs can be reduced. Accordingly, a liquid electrophotographic printer is usually provided with a carrier recovery apparatus for recovering a liquid carrier by collecting and condensing carrier vapor evaporated by the drying unit 20.
FIG. 2 is a schematic diagram illustrating a conventional carrier recovery apparatus provided near a drying unit in a liquid electrophotographic printer. Referring to FIG. 2, a drying unit 20 includes a drying roller 22, heating rollers 24 and a manifold 25. The drying roller 22 is disposed a predetermined distance from a guide roller 11 to be parallel with the guide roller 11, and absorbs a liquid carrier which adheres to a photoreceptor belt 10. The heating rollers 24 evaporate the liquid carrier absorbed by the drying roller 22. The manifold 25 collects the evaporated carrier vapor. In this case, some of the collected carrier vapor is liquefied and induced to a carrier recovery container 40 provided under the manifold 25, and the remaining carrier vapor is induced to a condenser 30.
The condenser 30 contains a low temperature liquid condensate. The upper portion of the condenser 30 is connected to an inflow pipe 31 through which the carrier vapor flows from the drying unit 20 into the condenser 30 and to a carrier vapor discharge pipe 34 through which uncondensed carrier vapor is discharged from the condenser 30. One side of the condenser 30 is connected to a carrier liquid discharge pipe 33 through which a condensed liquid carrier is discharged from the condenser 30. A peltier chip 44 is provided on another side of the condenser 30 to maintain a low temperature inside the condenser. Heat generated from the peltier chip 44 is effused to a heat sink 46.
Carrier vapor is induced from the drying unit 20 into the condenser 30 through the inflow pipe 31. Then, the carrier vapor contacts the liquid condensate to be liquefied. Uncondensed carrier vapor is induced through the carrier vapor discharge pipe 34 to a filter 35 and discharged to the outside through the filter 35. A liquid carrier condensed in the condenser 30 is discharged through the carrier liquid discharge pipe 33 to the carrier recovery container 40.
A first pump 32 for pumping carrier vapor out of the drying unit 20 into the condenser 30 is installed at a predetermined portion of the inflow pipe 31. A second pump 42 for supplying a liquid carrier collected within the carrier recovery container 40 to a development device (not shown) is installed at a predetermined portion of a carrier supply pipe 41. A third pump 52 for discharging carrier vapor is installed at a predetermined portion of the carrier vapor discharge pipe 34.
In a carrier recovery apparatus having such a structure, high temperature carrier vapor generated in the drying unit 20 may flow into the condenser 30 through the inflow pipe 31 without being cooled down appropriately, thereby decreasing the efficiency of condensing carrier vapor. Consequently, the recovery percentage of a carrier decreases. In addition, polluted carrier vapor which is not sufficiently filtered is discharged from the condenser 30, thereby shortening the duration of the filter 35.
To solve the above problems, it is an object of the present invention to provide a carrier recovery apparatus using a cooling unit with a radiator in a liquid electrophotographic printer to improve the efficiency of condensing carrier vapor, thereby increasing the recovery percentage of a carrier and extending the duration of a filter.
Accordingly, to achieve the above object of the invention, in one embodiment, there is provided a carrier recovery apparatus of a liquid electrophotographic printer, including a drying unit for absorbing and evaporating a liquid carrier remaining on a photoreceptor belt after development, a cooling unit for cooling and condensing carrier vapor evaporated by the drying unit, a condenser for cooling the carrier vapor which has passed through the cooling unit to condense the carrier vapor which has not been condensed by the cooling unit, and a carrier recovery container for storing a liquid carrier discharged from the condenser.
In another embodiment, there is provided a carrier recovery apparatus of a liquid electrophotographic printer, including a drying unit for absorbing and evaporating a liquid carrier remaining on a photoreceptor belt after development, a first cooling unit for cooling and condensing carrier vapor evaporated by the drying unit, a second cooling unit for cooling the carrier vapor which has passed through the first cooling unit to condense the carrier vapor which has not been condensed by the first cooling unit, a condenser for cooling the carrier vapor which has passed through the second cooling unit to condense the carrier vapor which has not been condensed by the first and second cooling units, and a carrier recovery container for storing a liquid carrier discharged from the condenser.